1. Field of the Invention
The invention relates to a modular system as a load-bearing frame to be disposed in the rear region of a motor vehicle.
2. Description of the Related Art
It is known that in the automotive industry, frames are used as a load-bearing lower framework for the motor vehicle superstructure. Such frames essentially form the main framework of the motor vehicle. Usually, the wheel suspension and the assemblies of the motor vehicle are attached to this frame. Known frames consist of two side members that are welded, riveted or screwed onto cross members and diagonal struts.
A distinction is made, in accordance with the shape of the frame, among ladder frames, X frames, platform frames, and lattice frames. In a ladder frame, the two side members are connected with one another by means of multiple cross members. Such a frame is predominantly used in trucks and SUVs. In what is called an X frame, two side members made of round or oval tubes approach one another in the center, to as little as a few centimeters, and appear as an X in a top view. In a platform frame, the car body floor is an integral part of the frame and is generally welded to the frame. This form of a frame is characterized by particularly great torsional rigidity and a low center of gravity. In a lattice frame, the frame parts are welded to one another in such a manner that they can form the base for the superstructure. A lattice frame is extremely torsion-resistant and is used in buses, sports cars, and racing cars.
In passenger cars, but also in buses, the self-supporting method of construction predominates today, in which instead of the frame, a floor group holds not only the load-bearing parts but also the trunk floor and the wheel boxes.
It is a disadvantage in some of the aforementioned frames or the floor group that they comprise a plurality of individual parts in the rear region of a motor vehicle, which must be joined together on site, in complicated, time-consuming and therefore cost-intensive manner. Not rarely, such frames or floor groups comprise more than 20 different individual parts, without including the required joining means in this number. It is a further disadvantage that some of the aforementioned frames and the said floor groups are configured in such a manner that they can be connected with chassis components, particularly with wheel suspensions such as steering arms, stabilizers, springs and/or dampers, only by way of a subframe, which is also referred to as an assembly support, axle support or auxiliary frame. Furthermore, the said frames or floor groups also have a relatively high weight, which has a negative effect on the fuel consumption of a motor vehicle. Furthermore, the said frames or floor groups, which have many connection points or joining locations, are more susceptible to production defects and can also have reduced mechanical properties with regard to a desired deformation behavior or a desired rigidity. The more connection points or joining locations there are, the greater the aforementioned deficits are.
Frames or floor groups as mentioned above are known to be complicated in their development and are generally tailored to a single vehicle type or a single vehicle series. A disadvantage of this is that individual parts that already exist often can no longer be used for a new vehicle type or a new vehicle series, and, in particular, the machines specifically procured and generally newly developed for their production can no longer be used, and therefore have to be newly procured or, if necessary, newly developed.